Advertisement

Advertisement

Human ancestors got a grip on tools 3 million years ago

MOVE over Homo habilis, you’re being dethroned. It seems our “handy” ancestor wasn’t the first to use stone tools. In fact, the apelike Australopithecus may have figured out how to handle them before modern humans evolved.

One of the first hints of this came in 2010, when German researchers working in Ethiopia discovered markings on two animal bones that were about 3.4 million years old. The cut marks had been made with a sharp stone, and the bones were at a site frequented by Lucy’s species, Australopithecus afarensis (see “timeline“).

But that study, led by Shannon McPherron of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, was controversial. The bones were 800,000 years older than the oldest uncontested stone tools, and at the time few thought that australopithecines had been tool users. Plus, McPherron hadn’t found the tool itself.

Advertisement

The problem, says McPherron, is that if we just go on tools that have been found, we must conclude that one day somebody made a beautifully flaked Oldowan hand axe, one of the oldest tools known, completely out of the blue. That is unlikely.

Now Matthew Skinner at the University of Kent, UK, and his colleagues have taken a different approach to dating tool use&colon; looking at the hands that held them. Specifically, they looked at metacarpal bones – the five bones in the palm of the hand that articulate the fingers. Because the bone ends are made of soft, spongy bone tissue, they are shaped over a lifetime of use and moulded by what a hand does.

A chimp, for instance, spends a lot of time swinging from branches and knuckle-walking, which exerts a great deal of force on the joints in its hands. Skinner and his colleagues predicted how this should shape the soft bone in ape hands, then looked at modern ape bones, finding their predictions were right.

Modern human metacarpals look different because we use our hands differently. Most of our activities involve some kind of pinching – think of how you hold a pen. This precision squeeze between thumb and fingers is uniquely human and a legacy from our flint-wielding ancestors.

When Skinner’s team looked at the metacarpals of early human species and Neanderthals – who also used stone flakes for tasks like scraping and butchering – they found bone ends that were shaped like modern human bones, and unlike ape bones.

Finally, they looked at metacarpals from four individuals of our ancestor Australopithecus africanus, which are up to 2.8 million years old (pictured). They revealed those individuals had been tree swingers but had also spent a lot of energy pinching small objects, suggesting they were indeed early tool users (Science, doi.org/znm).

A. africanus were tree swingers but they also pinched small objects, suggesting they had tools

“This study is really interesting because it shows how the hand was actually used, and that’s consistent with stone tool use,” says McPherron.

The similarities between A. africanus and human bones are relatively convincing, says John Hawks of the University of Wisconsin-Madison. “The best explanation is that the difference reflects some powerful thumb-to-finger gripping,” he says.

Whether that grip was used to manoeuvre delicate flakes of flint remains to be seen. It’s possible A. africanus used other types of tools, like bones or pieces of wood. Or they might have been using their precision grips to get at food, such as peeling tough skins off fruit – a task that chimps tend to do with their teeth.

But the study does suggest that 3 million years ago – 400,000 years before the oldest known hand axes – A. africanus was already starting to use its hands differently to its ancestors. They were more dexterous and more precise. Whether or not their hands were already wrapped around flints, they were at least laying the foundations for their descendants to do so.

Toolmaking timeline

3.4 million years ago

Where&colon; Dikika, Ethiopia

Species&colon;Australopithecus afarensis

Evidence&colon; Marks on animal bones suggest two types of tools&colon; a stone with a sharp edge that was used to cut and scrape, and a blunt tool that was used to crack the bones open and extract their marrow. But this is controversial as no one has found stone tools this old – yet.

2.8 – 2 million years ago

Where: South Africa

Species&colon;Australopithecus africanus

Evidence&colon; The shape of soft bone tissue in hand fossils suggests their owners had a tool-user’s grip (see main story). Still no tools found.

2.6 – 2.5 million years ago

Where: Gona, Ethiopia

Species: Unknown

Evidence&colon; The oldest undisputed stone tools are typical “Oldowan” style&colon; hammerstones that were used to crack hard objects, and stones that have been knapped to produce a sharp edge.

2.5 million years ago

Where: Bouri, Ethiopia

Species&colon; Unknown, possibly Australopithecus garhi

Evidence&colon; Cut marks and hammerstone fractures on animal bones suggest ancient humans were scraping and breaking them using stones.

This article appeared in print under the headline “The quiet rise of the first toolmaker”